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Cummins QSB 5.9 compared to QSC 8.3.

Discussion in 'Engines' started by John Spriggs, May 21, 2021.

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  1. John Spriggs, May 21, 2021
    #1
    John Spriggs

    John Spriggs Guest

    I understand the Cummins QSB 5.9 480hp has an excellent reputation for reliability and long life. 10,000 hours has been mentioned. Can any body say how it compares to the QSC 8.3 600hp, please?
  2. Capt J, May 21, 2021
    #2
    Capt J

    Capt J Senior Member

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    Both are very good motors. They both run very good. I feel the 8.3 has a lot more torque if going from the 480hp 5.9 to the 600hp 8.3. The 8.3's also tend to run smoother at slower speeds. The difference is size. 5.9 liters and 8.3 liters........ They've been producing both motors many years.
  3. Capt Ralph, May 22, 2021
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    I would consider the 5.9 rather strung out at 480hp. Like the 3208, you can only squeeze so much out of an onion.
    I also think the 8.3 is just getting it's legs moving at 500hp. Todays HO is 600hp. There was a 650hp but emissions forced Cummins to drop that back to 600.
  4. John Spriggs, May 23, 2021
    #4
    John Spriggs

    John Spriggs Guest

    Thanks guys. Anybody else had any experiences with these engines, please?
  5. GPO, May 23, 2021
    #5
    GPO

    GPO Member

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    I’m running QSC 8.3 HO 550’s on my Riviera 41 open fly bridge. LOA 46 beam 15. Advertised dry weight with standard engines 30,100 lbs. Make my weight with my engines, full fuel (2535 litres) and water (460 litres),water maker, larger house bank, zodiac tender, plus, plus, plus, conservatively closer to 40,000 lbs. 80% load at 2600 RPM, 21 KTS (vs advertised cruise 25 KTS with standard engines Cat C7 Acerts 460hp). No issues strictly following Cummins maintenance guidelines. No experience with QSB 5.9 480. Hope this helps.
  6. gr8trn, May 23, 2021
    #6
    gr8trn

    gr8trn Senior Member

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    QSB 5.9 380 hp variety for my boat. 40,000 dry.

    some would say underpowered application but I am happy with the application. Maybe related to hull design and Zeus pods.

    Starts, no smoke, smooth, temperature and oil pressure always spot on, coolant top off, Cummins recommended maintenance or more often.
    No complaints.
  7. Fishtigua, May 23, 2021
    #7
    Fishtigua

    Fishtigua Senior Member

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    Go large. We,ve had both and there's no saving on either.Man up and feel the burn.
  8. Capt Ralph, May 23, 2021
    #8
    Capt Ralph

    Capt Ralph Senior Member

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    Displacement always wins the endurance game.
  9. John Spriggs, May 24, 2021
    #9
    John Spriggs

    John Spriggs Guest

    Thank you, everybody. All that answers my question very nicely.
  10. 993RSR, May 24, 2021
    #10
    993RSR

    993RSR Senior Member

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    I am involved with a 2006 boat with twin 5.9's. Due to all the down time and poor maintenance the crankcase pressure is high and smoking on one side.
    I was told by the engine surveyor these motors are not not sleeved. True?
  11. ranger58sb, May 24, 2021
    #11
    ranger58sb

    ranger58sb Senior member

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    True.

    The 8.3s are sleeved.

    -Chris
  12. Fishtigua, May 24, 2021
    #12
    Fishtigua

    Fishtigua Senior Member

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    Sent 2 of our 5.9's back to the factory for a full rebuild. Worst $60k ever spent. Terrible job, sent them back.
  13. 993RSR, May 24, 2021
    #13
    993RSR

    993RSR Senior Member

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    Sure is nice being able to replace a piston and sleeve with the motor in the boat. Maybe the Cummins do not require that repair as often as Cats.
    Removing and reinstalling the motor can be 5x more expensive than the repair
  14. Capt J, May 24, 2021
    #14
    Capt J

    Capt J Senior Member

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    3208 cats weren't sleeved either and neither are yanmars as far as I know. Removing a 5.9 shouldn't be terribly difficult. Some boats labor might be less removing 5.9's because there's even less room to rebuild them in place. Cummins does have remans at a fair price with warranty.